Yes I agree 100% with Jim. It probably isn't a diverter as you would notice that when pump one runs by itself. It mist likely is low water. It will cause it to surge, or pulse as you say. Top it off a little bit with water, and I bet it goes away. If not, check your filter weir to make sure it isn't getting caught up on the filter, which can also cause it to surge. If those don't work, then call your dealer as Jim suggested.
Glad to hear you like your Arctic Spa Frontier! Enjoy!